package demo4;

import java.util.List;

public class MyLinkedList {
    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head ;
    public ListNode last ;


    //创建链表
    public void createList(){
        ListNode node1 = new ListNode(12);
        ListNode node2 = new ListNode(23);
        ListNode node3 = new ListNode(34);
        ListNode node4 = new ListNode(45);
        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        this.head = node1;
        this.last = node4;
    }


    //得到单链表的长度
    public int size(){
        ListNode cur = head;
        int count = 0;
        while (cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }

    //打印双链表
    public void display(){
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + "  ");
            cur = cur.next;
        }
        System.out.println();
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return  false;
    }

    //头插法
    public void addFirst(int data){
        ListNode cur = head;
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
            return;
        }
        node.next = head;
        head.prev = node;
        head = node;
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(last == null){
        last = node;
        head = node;
        return;
        }
        last.next = node;
        node.prev = last;
        last = last.next;

    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index < 0 || index > size()){
            throw new RuntimeException("index下标不合法！");
        }
        if(index == 0){
            //头插法
            addFirst(data);
        }
        if(index == size()){
            //尾插法
            addLast(data);
        }
        ListNode node = new ListNode(data);
        ListNode cur = head;
        //找到index下标！
        while(index != 0){
            cur = cur.next;
            index--;
        }
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                //开始删
                if(cur == head) {
                    //删除头节点
                    head = head.next;
                    //只要1个节点的时候
                    if(head != null) {
                        head.prev = null;
                    }else {
                        last = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next != null) {
                        //cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    }else {
                        //cur.prev.next = cur.next;
                        last = last.prev;
                    }
                }
                return;
            }else {
                cur = cur.next;
            }
        }
    }


    //删除所有值为key的节点
    public void removeAllKey(int key){ ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                //开始删
                if (cur == head) {
                    //删除头节点
                    head = head.next;
                    //只要1个节点的时候
                    if (head != null) {
                        head.prev = null;
                    }else {
                        last = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next != null) {
                        //cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    } else {
                        //cur.prev.next = cur.next;
                        last = last.prev;
                    }
                }
            }
            //cur = cur.next;
//            }else {
//                cur = cur.next;
//            }

            cur = cur.next;
        }
    }


    public void clear(){
        ListNode cur = head;
        while (cur != null) {
            ListNode curNext = cur.next;
            cur.prev = null;
            cur.next = null;
            //cur.val = null;
            cur = curNext;
        }
        head = null;
        last = null;
    }

}
